Luminary

Seventeen-year-old Caya Filar, like everyone else in her city, sees only in grayscale. Colors exist as magical energy, once worked by Luminaries like her father. But colors became something to fear when a prince, terrified of magic he couldn't see, slaughtered the Luminaries and stole the king's throne. 

Now little better than an outcast, Caya steers clear of the king's guards. She knows they're eager for any excuse to brand her a Luminary and execute her, whether she can see color or not. And there's no chance of leaving the city with guards patrolling the walls, murdering anyone who tries to flee. Keeping her head down, she works in a shop to feed her family—at least until the shopkeeper's son proposes. His respectable name might help her overcome the stigma left by her father's Luminary magic. 

If only the stone in her engagement ring had stayed gray. 

LUMINARY is a young adult fantasy complete at 91,000 words.